Roadwork is typically carried out by working machines that carry one or more working components and travel along a roadway. One such working machine is a milling machine, a wheeled or track-driven vehicle that is provided with a rotating working drum that includes a plurality of cutting teeth. The working drum is mounted in a housing on the frame of the machine and is adapted to be lowered into contact with the road surface and rotated about a generally horizontal axis so as to cut into the surface to a desired depth as the machine is advanced along the roadway. A milling machine includes a conveyor system typically comprising a conveyor that is designed to carry the milled material which has been cut from the roadway by the rotating drum to a location in front of, to the rear of, or beside the machine for deposit into a truck for removal from the milling site. Steerable track or wheel drive assemblies are provided to drive the working machine and to steer it in a desired working direction. Power for driving the milling machine and for operating all of its systems is typically provided by a diesel engine. Milled material cut from a roadway is quite abrasive, and its transport by the milling machine conveyor system abrades various wear components such as wear liners and the conveyor belting of the conveyor system. Other wear components such as chains, bearings, sprockets and idlers are worn by being subjected to loading during operation of the conveyor to move material during a period of time. These wear components must be inspected from time to time during the operating life of the milling machine and replaced when necessary. However, since the milling machine is a self-propelled vehicle that is driven to and from the milling site, and since the conveyor system is only operated while the milling drum is rotating, the operating time of the conveyor system under load is independent of the operating time of the drive engine.
When it is desired to pave a new roadway with asphalt paving materials, or when a milling operation has been completed in a roadway repair process, paving over the road base or milled roadway with asphalt paving material is generally carried out by another working machine, an asphalt paving machine. Asphalt paving material is comprised of an asphaltic binder and aggregates of various particle sizes, including both coarse and fine aggregate materials. Because the equipment needed to produce hot asphalt paving material, also called hot mix asphalt or “HMA”, is expensive and the space required extensive, HMA is typically produced in a production facility that is dedicated to such purpose. Consequently, it is frequently necessary to transport the HMA from its place of origin to an asphalt paving machine at a remote paving site. The HMA, at a temperature of up to 350° F., is transported in dump trucks to an asphalt paving machine or to another working machine, a material transfer vehicle that completes the transfer to the asphalt paving machine.
An asphalt paving machine is self-propelled and is driven by a wheeled or track drive system. In a common type of paving machine, an asphalt receiving hopper is located at the front end of the machine to receive asphalt paving material from a truck or material transfer vehicle, and a slat-type hopper conveyor located below the asphalt receiving hopper transfers the asphalt paving material from the hopper to a distribution assembly comprising a transverse distributing auger that is mounted at the rear of the machine. The asphalt paving material is deposited onto and across the roadway or other surface to be paved by the distributing auger, and a floating screed located behind the distributing auger compacts the asphalt paving material to form an asphalt mat. Asphalt paving material is hot and abrasive, and its transport by the paving machine conveyor system wears various components of the conveyor system, such as conveyor slats, side liners and floor liners, as well as the augers of the distribution assembly, during a paving operation. Other wear components of the conveyor system, such as chains, bearings, sprockets and idlers, are worn by being subjected to loading during operation of the conveyor to move asphalt paving material during a period of time. These wear components must be inspected from time to time during the operating life of the paving machine and replaced when necessary.
Sometimes, HMA is discharged directly from a delivery truck into the asphalt receiving hopper of the asphalt paving machine. When asphalt paving material is delivered to the paving machine in this manner, a series of delivery trucks must move into contact with the front end of the paving machine to serially discharge their loads into the paving machine hopper. This method of delivery requires multiple truck maneuvers that are often difficult to achieve without stopping the paving machine. However, when a paving machine stops and subsequently restarts, its floating screed will produce a dip in the asphalt mat (when the machine stops) and a bump (when it restarts). Consequently, a type of material transfer vehicle may be used to shuttle HMA between the delivery trucks and the asphalt paving machine. Yet another type of material transfer vehicle is adapted to move alongside the asphalt paving machine while being tethered to a delivery truck to allow for the transfer of asphalt paving material from a delivery truck to an asphalt paving machine without requiring either the delivery truck or the material transfer vehicle to make direct contact with the asphalt paving machine, thus reducing the time required for delivery truck maneuvers and reducing the risk that the paving machine will have to stop during the paving operation.
A self-propelled material transfer vehicle typically includes a large-capacity truck-receiving hopper and an inclined truck-unloading conveyor extending upwardly from this hopper. A transversely oriented auger is typically provided in the truck-receiving hopper to urge HMA onto the truck-unloading conveyor. This HMA is carried upwardly by the truck-unloading conveyor from the truck-receiving hopper and discharged off the elevated output end of the truck-unloading conveyor into a chute mounted on the lower end of a paver-loading conveyor (in a non-contact type of material transfer vehicle), or into an intermediate surge bin that is sized to hold the entire load of a delivery truck (in the type of material transfer vehicle that shuttles asphalt paving material from a pick-up point to a remote paving site). The discharge of HMA off the elevated output end of the truck-unloading conveyor so that it may fall under the influence of gravity into a chute or surge bin assists in preventing undesirable segregation of the various particulate components of the asphalt paving material by particle size.
Material transfer vehicles of the type that are equipped with a surge bin typically include an auger and a conveyor in the surge bin that are adapted to transfer the HMA to the paver-loading conveyor. Paver-loading conveyors mounted on material transfer vehicles with and without surge bins are generally pivotable about an essentially vertical axis so that the material transfer vehicle can be positioned alongside an asphalt paving machine that is laying an asphalt mat and rapidly discharge HMA into the hopper of the paving machine as the material transfer vehicle moves with the paving machine along the roadway. Because of its rapid loading and unloading capabilities, the type of material transfer vehicle that rapidly shuttles between delivery trucks at a pick-up point and an asphalt paving machine that is laying an asphalt mat at a paving site reduces the likelihood that the paving machine will have to stop paving because of a lack of asphalt paving material.
Because the conveyors of a material transfer vehicle do not have be operated simultaneously, and because a significant part of the engine operating time is devoted to moving the unloaded material transfer vehicle to a paving site, or to an asphalt paving material pick-up point from a paving site, it is difficult to predict from accumulated engine runtime when conveyor wear parts may need to be replaced. Furthermore, for a material transfer vehicle that is equipped with a surge bin, i.e., a three-conveyor machine, the truck-unloading conveyor and its associated auger can operate independently of the surge bin conveyor and the paver-loading conveyor. In addition, the paver-loading conveyor can operate independently of the truck-unloading conveyor or the surge bin conveyor; however, the paver-loading conveyor has to be “on” for the surge bin conveyor to operate. For a material transfer vehicle that is not equipped with a surge bin, i.e., a two-conveyor machine, the paver-loading conveyor can operate independently of the truck-unloading conveyor, but the paver-loading conveyor has to be “on” for the truck-unloading conveyor to operate.
As has been mentioned, asphalt paving materials are quite abrasive, and may be delivered to a material transfer vehicle at temperatures of up to 350° F. Consequently, several of the components of the conveyor system, such as conveyor slats, side liners and floor liners, are intended to be replaced as necessary due to frictional forces generated by the hot mix asphalt paving material. Other components of the conveyor system of a material transfer vehicle will also need to be replaced from time to time, including conveyor chains, sprockets, idlers and bearings associated with the conveyors. In addition, the augers in the truck-receiving hopper and the surge bin also wear out over time and may need to be replaced.
Cold in-place recycling (“CIR”) equipment can be used to repair damage to a roadway in a single pass, while reusing essentially all of the existing asphalt pavement in the damaged areas. In the CIR process, damaged layers of asphalt pavement are removed. The removed material is processed and replaced on the roadway and then compacted. If a roadway has good structural strength, a CIR process can be effective for treating all types of cracking, ruts and holes in asphalt pavement. CIR can be used to repair asphalt roadways damaged by fatigue (alligator) cracking, bleeding (of excess asphalt cement), block cracking, corrugation and shoving, joint reflective cracking, longitudinal cracking, patching, polished aggregate, potholes, raveling, rutting, slippage cracking, stripping and transverse (thermal) cracking. The root cause of the pavement failure should always be investigated to rule out base failure. However, CIR can almost always be used when there is no damage to the base of the roadway. Generally, CIR is only half as expensive as paving with HMA, while providing approximately 80% of the strength of hot mix paving.
CIR can be carried out with the aid of a milling machine that has been modified by mounting a spray assembly in the milling drum housing to inject asphalt cement into the milling drum housing. The asphalt cement is then thoroughly blended with the milled material by the milling drum and can be left in a windrow or fed by the milling machine's discharge conveyor directly into an asphalt paving machine. When the CIR process is carried out with only a milling machine and an asphalt paving machine, the asphalt cement component of the cold mix asphalt (“CMA”) must be supplied from a separate supply tank truck that is coupled to the modified milling machine. The asphalt cement component is drawn directly from the tank on the supply truck and metered through a flow system that is mounted on the milling machine to the spray assembly in the milling drum housing. The operation of the conveyor system of a modified milling machine to transport milled material and CMA comprising the recycled asphalt paving material mixed with asphalt cement abrades various wear components such as wear liners and belting of the conveyor system. Other wear components such as chains, bearings, sprockets and idlers are worn by being subjected to loading over a period of time. These wear components must be inspected from time to time during the operating life of the modified milling machine and replaced when necessary.
Sometimes the CIR process is carried out with a milling machine in train with a cold recycler machine such as the RT-500 that is made and sold by Roadtec, Inc. of Chattanooga, Tenn. The cold recycler machine may include a vibratory screen, a crusher, an onboard source of asphalt cement and a pugmill mixer, along with various conveyors. When the CIR process is carried out using a cold recycler machine, the recycled asphalt material that is milled by the milling machine is transferred to the vibratory screen and then to the crusher on the cold recycler machine, and the screened and crushed material is then mixed with asphalt cement that is dispensed by a spray assembly from an onboard supply tank into the pugmill to produce CMA. The CMA that is produced by this process can be left in a windrow on the roadway or fed by the cold recycler machine's discharge conveyor directly into an asphalt paving machine. The operation of the conveyor system of a cold recycler machine to transport milled material and CMA comprising the recycled asphalt paving material mixed with asphalt cement abrades various wear components such as wear liners and belting of the conveyor system. Other wear components such as chains, bearings, sprockets and idlers are worn by being subjected to loading over a period of time. These wear components must be inspected from time to time during the operating life of the cold recycler machine and replaced when necessary.
It would be desirable if a system could be developed that could accurately measure the time that each conveyor of a working machine is used to carry asphalt paving material or milled material and to provide notice when certain wear parts, including conveyor belting, chains and slats, conveyor floor liners and side liners, sprockets, idlers, bearings and augers should be replaced or inspected for possible replacement.